1. Field of the Invention
The present invention relates to a semiconductor integrated circuit including a mixer, and a wireless communication apparatus including the semiconductor integrated circuit.
2. Description of the Related Art
In a GSM (Global System For Mobile Communications) transmitter or a WCDMA (Wideband Code Division Multiple Access) transmitter, specifications of receiving band noise of a low level must be satisfied, and a transmitting spectrum must be in a regulation spectrum mask by satisfying low distortion requirements.
Generally, a transmitter is designed so that a transmitting spectrum is in a regulation spectrum mask. Furthermore, a receiving band noise level is decreased by inserting a SAW (Surface Acoustic Wave) filter etc. in a transmitter output.
However, in a transmitter, it will be mainstream in the future to reduce chip external devices, especially SAW filters, so as to reduce an implementation area and costs for the purpose of enhancement of competitiveness.
The specification of receiving band noise of a low level will still be applied in the future, while also desiring to reduce an implementation area. Actually, in a conference presentation, a WCDMA transmitter aiming at reducing SAW filters has been reported.
To reduce the receiving band noise of a transmitter, it is known to raise the gain of a transmitter. However, generating spurious signals in a transmitter increases when a gain is raised. A transmitting spectrum may not then fall in a regulation spectrum mask. That is, noise and distortion have the relation of a trade-off, and it is difficult to realize both of low noise and low distortion simultaneously.